US20150330058A1 - Method for controlling hydraulic system for construction machine - Google Patents

Method for controlling hydraulic system for construction machine Download PDF

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Publication number
US20150330058A1
US20150330058A1 US14/410,987 US201214410987A US2015330058A1 US 20150330058 A1 US20150330058 A1 US 20150330058A1 US 201214410987 A US201214410987 A US 201214410987A US 2015330058 A1 US2015330058 A1 US 2015330058A1
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working device
working
devices
hydraulic
operation lever
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US14/410,987
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Sang-Hee Lee
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Volvo Construction Equipment AB
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Volvo Construction Equipment AB
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Assigned to VOLVO CONSTRUCTION EQUIPMENT AB reassignment VOLVO CONSTRUCTION EQUIPMENT AB ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LEE, SANG-HEE
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2239—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance
    • E02F9/2242—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance including an electronic controller
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/2004—Control mechanisms, e.g. control levers
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2232—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
    • E02F9/2235—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps including an electronic controller
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2282—Systems using center bypass type changeover valves
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2285—Pilot-operated systems
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2292—Systems with two or more pumps
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2296—Systems with a variable displacement pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/022—Systems essentially incorporating special features for controlling the speed or actuating force of an output member in which a rapid approach stroke is followed by a slower, high-force working stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/166—Controlling a pilot pressure in response to the load, i.e. supply to at least one user is regulated by adjusting either the system pilot pressure or one or more of the individual pilot command pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/17—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors using two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
    • F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
    • F15B13/0435—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves the pilot valves being sliding valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/3059—Assemblies of multiple valves having multiple valves for multiple output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/3059—Assemblies of multiple valves having multiple valves for multiple output members
    • F15B2211/30595—Assemblies of multiple valves having multiple valves for multiple output members with additional valves between the groups of valves for multiple output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
    • F15B2211/31594—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having multiple pressure sources and multiple output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6346—Electronic controllers using input signals representing a state of input means, e.g. joystick position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6652—Control of the pressure source, e.g. control of the swash plate angle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6654—Flow rate control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7135—Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/78—Control of multiple output members

Definitions

  • the present invention relates to a method for controlling a hydraulic system for a construction machine. More particularly, the present invention relates to a method for controlling a hydraulic system for a construction machine is disclosed, which can minimize a loss of pressure through expansion of an open area of a confluence spool in the case of singly driving a working device such as a boom in the hydraulic system provided with a plurality of hydraulic pumps and the confluence spool.
  • a hydraulic system for a construction machine to which the present invention is applied includes an engine 1 ; first and second variable displacement hydraulic pumps (hereinafter referred to as a “first and second hydraulic pumps”) 2 and 3 connected to the engine 1 and a pilot pump 4 ; a first working device (not illustrated), such as a boom, connected to the first hydraulic pump 2 through a discharge flow path 2 a to be driven when hydraulic fluid is supplied thereto; a second working device (not illustrated), such as an arm, connected to the second hydraulic pump 3 through a discharge flow path 3 a to be driven when hydraulic fluid is supplied thereto; an operation lever (RCV) 5 for the first working device outputting an operation signal that corresponds to an operation amount by an operator; an operation lever (RCV) 6 for the second working device outputting an operation signal that corresponds to an operation amount by the operator; a main control valve provided with spools 7 and 8 for the first and second working devices shifted by the operations of the operation levers 5 and 6 for the first and second working devices to control the
  • the unexplained reference numeral 20 denotes a graph of a control diagram of the second hydraulic pump 3 during a combined operation of the operation lever 5 for the first working device and the operation lever 6 for the second working device.
  • pilot signal pressure that is discharged from the pilot pump 4 is supplied to the spool 7 for the first working device to shift the spool 7 in a rightward direction in the drawing.
  • the pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11 .
  • the hydraulic fluid that is discharged from the first hydraulic pump 2 to correspond to the operation amount of the operation lever 5 for the first working device is supplied to the boom cylinder (not illustrated) via the discharge flow path 2 a , the spool 7 for the first working device, and a flow path 15 in order.
  • the controller 11 outputs a control signal for controlling the electro-proportional valve 14 .
  • a control diagram 17 of FIG. 2 to control a shift amount of the confluence spool 9 , the confluence spool 9 is shifted in the leftward direction in FIG. 1 by the pilot signal pressure that is supplied from the pilot pump 4 .
  • the secondary signal pressure as high as “b 1 ” is supplied to the confluence spool 9 in proportion to “a 1 ”
  • the secondary signal pressure as high as “b 2 ” is supplied to the confluence spool 9 in proportion to “a 2 ”.
  • the second hydraulic pump 3 discharges the hydraulic fluid that is in proportion to the operation amount of the operation lever 5 for the first working device. That is, if the operation amount of the operation lever 5 for the first working device is “c 1 ”, the second hydraulic pump 3 discharges the hydraulic fluid as much as “d 1 ” in proportion to “c 1 ”, while if the operation amount is “c 2 ”, the second hydraulic pump 3 discharges the hydraulic fluid as much as “d 2 ” in proportion to “c 2 ”.
  • the hydraulic fluid that is discharged from the second hydraulic pump 3 passes through the discharge flow path 3 a , the confluence spool 9 , and a confluence flow path 16 in order, and then joins the hydraulic fluid that is discharged from the first hydraulic pump 2 to the flow path 15 .
  • control diagram 17 illustrated in FIG. 2 to control the confluence spool 9 is equally applied to not only single driving of a boom-up operation but also a combined operation of working devices, such as a boom and an arm, through shifting of the spool 8 for the second working device.
  • the other working device does not use the hydraulic fluid of the first and second hydraulic pumps 2 and 3 , and thus the hydraulic fluid that is discharged from the first and second hydraulic pumps 2 and 3 is used only for the boom-up operation. That is, in the case of singly performing the boom-up operation, the hydraulic fluid that is supplied to the boom cylinder can be controlled only by the control of the first and second hydraulic pump 2 and 3 . Accordingly, in the case of the single boom-up operation, an open area of the confluence spool 9 is controlled to become small, and thus the control that causes a loss of pressure in the confluence spool 9 becomes unnecessary.
  • one embodiment of the present invention is related to a method for controlling a hydraulic system for a construction machine, which can heighten the fuel efficiency by minimizing a loss of pressure that is generated in a confluence spool through expansion of an open area of the confluence spool in the case of singly driving a working device such as a boom rather than in the case of a combined operation of working devices.
  • a method for controlling a hydraulic system for a construction machine including first and second hydraulic pumps connected to an engine, a pilot pump, first and second working devices connected to the first and second hydraulic pumps to be driven, operation levers for the first and second working devices outputting operation signals that correspond to the operation amounts, spools for the first and second work devices shifted by operations of the operation levers for the first and second working devices to control hydraulic fluid supplied to the first and second working devices, a main control valve having a confluence spool that makes hydraulic fluid of the second hydraulic pump and hydraulic fluid of the first hydraulic pump join together, a controller, first and second pressure sensing devices detecting operation signals of the operation levers for the first and second working devices, and an electro-proportional valve converting pilot signal pressure that is supplied to the confluence spool into secondary signal pressure corresponding to a control signal from the controller, the method includes a first step of detecting pilot signals according to the operations of the operation levers for the first and second working devices through the first and
  • electronic operation levers may be used as the operation levers for the first and second working devices.
  • the method for controlling a hydraulic system for a construction machine has the following advantages.
  • the loss of pressure that is generated in the confluence spool can be minimized through expansion of the open area of the confluence spool in comparison to the case of the combined driving, and thus the fuel efficiency of the equipment can be heightened.
  • FIG. 1 is a hydraulic circuit diagram of a hydraulic system for a construction machine to which the present invention is applied;
  • FIG. 2 is a flowchart illustrating a method for controlling a hydraulic system for a construction machine in the related art
  • FIG. 3 is a flowchart illustrating a method for controlling a hydraulic system for a construction machine according to an embodiment of the present invention.
  • FIG. 4 is a graph showing correlation between secondary pressure of an electro-proportional valve and an open area of a confluence valve in a method for controlling a hydraulic system for a construction machine according to an embodiment of the present invention.
  • a method for controlling a hydraulic system for a construction machine including an engine 1 ; first and second variable displacement hydraulic pumps (hereinafter referred to as a “first and second hydraulic pumps”) 2 and 3 connected to the engine 1 and a pilot pump 4 ; a first working device, such as a boom, connected to the first hydraulic pump 2 through a discharge flow path 2 a to be driven when hydraulic fluid is supplied thereto; a second working device, such as an arm, connected to the second hydraulic pump 3 through a discharge flow path 3 a to be driven when hydraulic fluid is supplied thereto; an operation lever 5 for the first working device outputting an operation signal that corresponds to an operation amount by an operator; an operation lever 6 for the second working device outputting an operation signal that corresponds to an operation amount by the operator; a main control valve provided with spools 7 and 8 for the first and second working devices shifted by the operations of the operation levers 5 and 6 for the first and second working devices to control
  • electronic operation levers may be used as the operation levers 5 and 6 for the first and second working devices.
  • pilot signal pressure that is discharged from the pilot pump 4 is supplied to the spool 7 for the first working device to shift the spool 7 in a rightward direction in the drawing.
  • the pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11 .
  • the hydraulic fluid that is discharged from the first hydraulic pump 2 to correspond to the operation amount of the operation lever 5 for the first working device is supplied to the boom cylinder via the discharge flow path 2 a , the spool 7 for the first working device, and a flow path 15 in order.
  • pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11 .
  • control diagrams 17 and 19 of FIG. 3 to control the electro-proportional valve 14 , if the pilot signal pressure that is detected by the first pressure sensing device 12 is higher than pilot pressure a 1 by the operation of the operation lever 5 for the first working device, the controller 11 controls the electro-proportional valve 14 as shown in a control diagram 19 .
  • the difference between the control diagrams 17 and 19 is that the slope of the secondary pressure for controlling the electro-proportional valve 14 of the control diagram 19 becomes higher than the slope of the secondary pressure for controlling the electro-proportional valve 14 of the control diagram 17 . Due to this, as shown in FIG. 4 , a larger open area of the confluence spool 9 for the first working device is secured with respect to the same pilot pressure of the operation lever 5 for the first working device.
  • the hydraulic fluid that is discharged from the second hydraulic pump 3 as shown in the control diagram 18 of FIG. 3 becomes equal to the discharge amount when the operation lever 5 for the first working device is singly driven. That is, the loss of pressure in the confluence spool 9 for the first working device becomes smaller with respect to the same operation amount of the operation lever 5 for the first working device.
  • the pilot signal that is detected by the second pressure sensing device 13 is transmitted to the controller 11 , and thus the controller 11 determines that a combined operation of the working devices is performed through simultaneous operation of the operation levers 5 and 6 for the first and second working devices.
  • the electro-proportional valve 14 is controlled by the control signal from the controller 11 as shown in the control diagram 17 of FIG. 3 .
  • the discharge flow rate of the second hydraulic pump 3 becomes the sum of the flow rates that are required by the first working device (e.g., boom cylinder) and the second working device (e.g., arm cylinder) as shown in the control diagram 20 of FIG. 3 .
  • a loss of pressure that is generated in a confluence spool can be minimized through expansion of an open area of the confluence spool in the case of singly driving a working device such as a boom rather than in the case of a combined operation of working devices.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Operation Control Of Excavators (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

A method for controlling a hydraulic system for a construction machine is disclosed, which can minimize a loss of pressure through expansion of an open area of a confluence spool in the case of singly driving a working device such as a boom. The method for controlling a hydraulic system includes a first step of detecting pilot signals according to operations of operation levers for first and second working devices through first and second pressure sensing devices and transmitting the detected pilot signals to the controller; a second step of determining whether the operation is a single operation of the operation lever for the first working device; a third step of supplying secondary signal pressure by an electro-proportional value to the confluence spool to expand an open area of the confluence spool with respect to the same operation pressure of the operation lever for the first working device and discharging hydraulic fluid discharged from a second hydraulic pump in proportion to the operation amount of the operation lever for the first working device if the operation lever for the first working device is operated to exceed a determined section in the case of singly driving the first working device due to the single operation of the operation lever for the first working device; and a fourth step of supplying the secondary signal pressure by the electro-proportional value to the confluence spool in proportion to the operation amount of the operation lever for the first working device and dividedly supplying the hydraulic fluid discharged from the second hydraulic pump to the first and second working devices in the case of performing a combined driving of the first and second working devices due to simultaneous operations of the operation levers for the first and second working devices.

Description

    TECHNICAL FIELD
  • The present invention relates to a method for controlling a hydraulic system for a construction machine. More particularly, the present invention relates to a method for controlling a hydraulic system for a construction machine is disclosed, which can minimize a loss of pressure through expansion of an open area of a confluence spool in the case of singly driving a working device such as a boom in the hydraulic system provided with a plurality of hydraulic pumps and the confluence spool.
    • BACKGROUND ART
  • A hydraulic system for a construction machine to which the present invention is applied, as illustrated in FIG. 1, includes an engine 1; first and second variable displacement hydraulic pumps (hereinafter referred to as a “first and second hydraulic pumps”) 2 and 3 connected to the engine 1 and a pilot pump 4; a first working device (not illustrated), such as a boom, connected to the first hydraulic pump 2 through a discharge flow path 2 a to be driven when hydraulic fluid is supplied thereto; a second working device (not illustrated), such as an arm, connected to the second hydraulic pump 3 through a discharge flow path 3 a to be driven when hydraulic fluid is supplied thereto; an operation lever (RCV) 5 for the first working device outputting an operation signal that corresponds to an operation amount by an operator; an operation lever (RCV) 6 for the second working device outputting an operation signal that corresponds to an operation amount by the operator; a main control valve provided with spools 7 and 8 for the first and second working devices shifted by the operations of the operation levers 5 and 6 for the first and second working devices to control the hydraulic fluid supplied from the first and second hydraulic pumps 2 and 3 to the first and second working devices, and a confluence spool 9 shifted by the operation of the operation lever 5 for the first working device to make the hydraulic fluid of the second hydraulic pump 3 and the hydraulic fluid of the first hydraulic pump 2 join together; a controller 11; a first pressure sensing device 12 detecting the operation signal of the operation lever 5 for the first working device and transmitting a detected pilot signal to the controller 11; a second pressure sensing device 13 detecting the operation signal of the operation lever 6 for the second working device and transmitting a detected pilot signal to the controller 11; and an electro-proportional valve 14 converting pilot signal pressure that is supplied from the pilot pump 4 to the confluence spool 9 into secondary signal pressure corresponding to a control signal from the controller 11.
  • In the drawing, the unexplained reference numeral 20 denotes a graph of a control diagram of the second hydraulic pump 3 during a combined operation of the operation lever 5 for the first working device and the operation lever 6 for the second working device.
  • In the hydraulic system for a construction machine as configured above, if an operator operates the operation lever 5 for the first working device for boom-up operation, pilot signal pressure that is discharged from the pilot pump 4 is supplied to the spool 7 for the first working device to shift the spool 7 in a rightward direction in the drawing. In this case, the pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11.
  • Through this, the hydraulic fluid that is discharged from the first hydraulic pump 2 to correspond to the operation amount of the operation lever 5 for the first working device is supplied to the boom cylinder (not illustrated) via the discharge flow path 2 a, the spool 7 for the first working device, and a flow path 15 in order.
  • In this case, if the operator increases the stroke of the operation lever 5 for the first working device for faster boom-up operation of the boom cylinder, the controller 11 outputs a control signal for controlling the electro-proportional valve 14. As shown in a control diagram 17 of FIG. 2 to control a shift amount of the confluence spool 9, the confluence spool 9 is shifted in the leftward direction in FIG. 1 by the pilot signal pressure that is supplied from the pilot pump 4. That is, if the operation amount of the operation lever 5 for the first working device is “a1”, the secondary signal pressure as high as “b1” is supplied to the confluence spool 9 in proportion to “a1”, while if the operation amount is “a2”, the secondary signal pressure as high as “b2” is supplied to the confluence spool 9 in proportion to “a2”.
  • Through this, as shown in a control diagram 18 of FIG. 2, the second hydraulic pump 3 discharges the hydraulic fluid that is in proportion to the operation amount of the operation lever 5 for the first working device. That is, if the operation amount of the operation lever 5 for the first working device is “c1”, the second hydraulic pump 3 discharges the hydraulic fluid as much as “d1” in proportion to “c1”, while if the operation amount is “c2”, the second hydraulic pump 3 discharges the hydraulic fluid as much as “d2” in proportion to “c2”. Through this, the hydraulic fluid that is discharged from the second hydraulic pump 3 passes through the discharge flow path 3 a, the confluence spool 9, and a confluence flow path 16 in order, and then joins the hydraulic fluid that is discharged from the first hydraulic pump 2 to the flow path 15.
  • On the other hand, the control diagram 17 illustrated in FIG. 2 to control the confluence spool 9 is equally applied to not only single driving of a boom-up operation but also a combined operation of working devices, such as a boom and an arm, through shifting of the spool 8 for the second working device.
  • In the case of singly performing the boom-up operation, the other working device (such as the arm) does not use the hydraulic fluid of the first and second hydraulic pumps 2 and 3, and thus the hydraulic fluid that is discharged from the first and second hydraulic pumps 2 and 3 is used only for the boom-up operation. That is, in the case of singly performing the boom-up operation, the hydraulic fluid that is supplied to the boom cylinder can be controlled only by the control of the first and second hydraulic pump 2 and 3. Accordingly, in the case of the single boom-up operation, an open area of the confluence spool 9 is controlled to become small, and thus the control that causes a loss of pressure in the confluence spool 9 becomes unnecessary.
  • That is, according to the method for controlling a hydraulic system for a construction machine in the related art, since the open area of the confluence spool 9 is controlled to become small during the single boom-up operation, unnecessary pressure loss occurs due to metering of the confluence spool 9, and this causes a loss of the fuel efficiency of the equipment.
    • DISCLOSURE Technical Problem
  • Therefore, the present invention has been made to solve the above-mentioned problems occurring in the related art, and one embodiment of the present invention is related to a method for controlling a hydraulic system for a construction machine, which can heighten the fuel efficiency by minimizing a loss of pressure that is generated in a confluence spool through expansion of an open area of the confluence spool in the case of singly driving a working device such as a boom rather than in the case of a combined operation of working devices.
    • Technical Solution
  • In accordance with an aspect of the present invention, there is provided a method for controlling a hydraulic system for a construction machine including first and second hydraulic pumps connected to an engine, a pilot pump, first and second working devices connected to the first and second hydraulic pumps to be driven, operation levers for the first and second working devices outputting operation signals that correspond to the operation amounts, spools for the first and second work devices shifted by operations of the operation levers for the first and second working devices to control hydraulic fluid supplied to the first and second working devices, a main control valve having a confluence spool that makes hydraulic fluid of the second hydraulic pump and hydraulic fluid of the first hydraulic pump join together, a controller, first and second pressure sensing devices detecting operation signals of the operation levers for the first and second working devices, and an electro-proportional valve converting pilot signal pressure that is supplied to the confluence spool into secondary signal pressure corresponding to a control signal from the controller, the method includes a first step of detecting pilot signals according to the operations of the operation levers for the first and second working devices through the first and second pressure sensing devices and transmitting the detected pilot signals to the controller; a second step of determining whether the operation is a single operation of the operation lever for the first working device; a third step of supplying secondary signal pressure by the electro-proportional value to the confluence spool to expand an open area of the confluence spool with respect to the same operation pressure of the operation lever for the first working device and discharging hydraulic fluid discharged from the second hydraulic pump in proportion to the operation amount of the operation lever for the first working device if the operation lever for the first working device is operated to exceed a determined section in the case of singly driving the first working device due to the single operation of the operation lever for the first working device; and a fourth step of supplying the secondary signal pressure by the electro-proportional value to the confluence spool in proportion to the operation amount of the operation lever for the first working device and dividedly supplying the hydraulic fluid discharged from the second hydraulic pump to the first and second working devices in the case of performing a combined driving of the first and second working devices due to simultaneous operations of the operation levers for the first and second working devices.
  • Preferably, electronic operation levers may be used as the operation levers for the first and second working devices.
    • Advantageous Effect
  • The method for controlling a hydraulic system for a construction machine according to the aspect of the present invention has the following advantages.
  • In the case of singly driving a working device, such as boom-up driving, the loss of pressure that is generated in the confluence spool can be minimized through expansion of the open area of the confluence spool in comparison to the case of the combined driving, and thus the fuel efficiency of the equipment can be heightened.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • The above objects, other features and advantages of the present invention will become more apparent by describing the preferred embodiments thereof with reference to the accompanying drawings, in which:
  • FIG. 1 is a hydraulic circuit diagram of a hydraulic system for a construction machine to which the present invention is applied;
  • FIG. 2 is a flowchart illustrating a method for controlling a hydraulic system for a construction machine in the related art;
  • FIG. 3 is a flowchart illustrating a method for controlling a hydraulic system for a construction machine according to an embodiment of the present invention; and
  • FIG. 4 is a graph showing correlation between secondary pressure of an electro-proportional valve and an open area of a confluence valve in a method for controlling a hydraulic system for a construction machine according to an embodiment of the present invention.
    •  DESCRIPTION OF REFERENCE NUMERALS IN THE DRAWING
      • 1: engine
      • 2: first variable displacement hydraulic valve
      • 3: second variable displacement hydraulic valve
      • 4: pilot pump
      • 5: operation lever for a first working device
      • 6: operation lever for a second working device
      • 7: spool for a first working device
      • 8: spool for a second working device
      • 9: confluence spool
      • 10: main control valve (MCV)
      • 11: controller
      • 12: first pressure sensing device
      • 13: second pressure sensing device
      • 14: electro-proportional valve
      • 15: flow path
      • 16: confluence flow path
    BEST MODE
  • Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and the present invention is not limited to the embodiments disclosed hereinafter.
  • According to an embodiment of the present invention, referring to FIGS. 1, 3, and 4, a method for controlling a hydraulic system for a construction machine including an engine 1; first and second variable displacement hydraulic pumps (hereinafter referred to as a “first and second hydraulic pumps”) 2 and 3 connected to the engine 1 and a pilot pump 4; a first working device, such as a boom, connected to the first hydraulic pump 2 through a discharge flow path 2 a to be driven when hydraulic fluid is supplied thereto; a second working device, such as an arm, connected to the second hydraulic pump 3 through a discharge flow path 3 a to be driven when hydraulic fluid is supplied thereto; an operation lever 5 for the first working device outputting an operation signal that corresponds to an operation amount by an operator; an operation lever 6 for the second working device outputting an operation signal that corresponds to an operation amount by the operator; a main control valve provided with spools 7 and 8 for the first and second working devices shifted by the operations of the operation levers 5 and 6 for the first and second working devices to control the hydraulic fluid supplied from the first and second hydraulic pumps 2 and 3 to the first and second working devices, and a confluence spool 9 shifted by the operation of the operation lever 5 for the first working device to make the hydraulic fluid of the second hydraulic pump 3 and the hydraulic fluid of the first hydraulic pump 2 join together; a controller 11; a first pressure sensing device 12 detecting the operation signal of the operation lever 5 for the first working device and transmitting a detected pilot signal to the controller 11; a second pressure sensing device 13 detecting the operation signal of the operation lever 6 for the second working device and transmitting a detected pilot signal to the controller 11; and an electro-proportional valve 14 converting pilot signal pressure that is supplied from the pilot pump 4 to the confluence spool 9 into secondary signal pressure corresponding to a control signal from the controller 11, includes a first step (S100) of detecting pilot signals according to the operations of the operation levers 5 and 6 for the first and second working devices through the first and second pressure sensing devices 12 and 13 and transmitting the detected pilot signals to the controller 11; a second step (S200) of determining whether the operation is a single operation of the operation lever 5 for the first working device; a third step (S300: S300A and S300B) of supplying secondary signal pressure by the electro-proportional value 14 to the confluence spool 9 to expand an open area of the confluence spool 9 with respect to the same operation pressure of the operation lever 5 for the first working device and discharging hydraulic fluid discharged from the second hydraulic pump 3 in proportion to the operation amount of the operation lever 5 for the first working device if the operation lever 5 for the first working device is operated to exceed a determined section in the case of singly driving the first working device due to the single operation of the operation lever 5 for the first working device; and a fourth step (S400: S400A and S400B) of supplying the secondary signal pressure by the electro-proportional value 14 to the confluence spool 9 in proportion to the operation amount of the operation lever 5 for the first working device and dividedly supplying the hydraulic fluid discharged from the second hydraulic pump 3 to the first and second working devices in the case of performing a combined driving of the first and second working devices due to simultaneous operations of the operation levers 5 and 6 for the first and second working devices.
  • Preferably, electronic operation levers may be used as the operation levers 5 and 6 for the first and second working devices.
  • Hereinafter, a use example of the method for controlling a hydraulic system for a construction machine according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
  • As shown in FIGS. 1, 3, and 4, if an operator operates the operation lever 5 for the first working device for boom-up operation, pilot signal pressure that is discharged from the pilot pump 4 is supplied to the spool 7 for the first working device to shift the spool 7 in a rightward direction in the drawing. In this case, the pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11. Accordingly, the hydraulic fluid that is discharged from the first hydraulic pump 2 to correspond to the operation amount of the operation lever 5 for the first working device is supplied to the boom cylinder via the discharge flow path 2 a, the spool 7 for the first working device, and a flow path 15 in order.
  • In this case, if the operator increases the stroke of the operation lever 5 for the first working device for faster boom-up operation of the boom cylinder, pilot signal pressure that is detected by the first pressure sensing device 12 is transmitted to the controller 11.
  • In this case, as shown in control diagrams 17 and 19 of FIG. 3 to control the electro-proportional valve 14, if the pilot signal pressure that is detected by the first pressure sensing device 12 is higher than pilot pressure a1 by the operation of the operation lever 5 for the first working device, the controller 11 controls the electro-proportional valve 14 as shown in a control diagram 19.
  • In this case, the difference between the control diagrams 17 and 19 is that the slope of the secondary pressure for controlling the electro-proportional valve 14 of the control diagram 19 becomes higher than the slope of the secondary pressure for controlling the electro-proportional valve 14 of the control diagram 17. Due to this, as shown in FIG. 4, a larger open area of the confluence spool 9 for the first working device is secured with respect to the same pilot pressure of the operation lever 5 for the first working device.
  • In this case, the hydraulic fluid that is discharged from the second hydraulic pump 3 as shown in the control diagram 18 of FIG. 3 becomes equal to the discharge amount when the operation lever 5 for the first working device is singly driven. That is, the loss of pressure in the confluence spool 9 for the first working device becomes smaller with respect to the same operation amount of the operation lever 5 for the first working device.
  • On the other hand, in the case of operating the operation lever 6 for the second working device, the pilot signal that is detected by the second pressure sensing device 13 is transmitted to the controller 11, and thus the controller 11 determines that a combined operation of the working devices is performed through simultaneous operation of the operation levers 5 and 6 for the first and second working devices.
  • Accordingly, the electro-proportional valve 14 is controlled by the control signal from the controller 11 as shown in the control diagram 17 of FIG. 3. In this case, the discharge flow rate of the second hydraulic pump 3 becomes the sum of the flow rates that are required by the first working device (e.g., boom cylinder) and the second working device (e.g., arm cylinder) as shown in the control diagram 20 of FIG. 3.
  • That is, since the hydraulic fluid discharged from the first and second hydraulic pumps 2 and 3 is distributed and supplied to the first and second working devices (this is the same as the hydraulic system that distributes and supplies the hydraulic fluid from the first and second hydraulic pumps to the first and second working devices during the combined operation in the related art), this does not interfere with the operation performance during the combined operation in the related art, and the fuel efficiency of the equipment can be improved only in the case of the single operation.
    • INDUSTRIAL APPLICABILITY
  • As apparent from the above description, according to the present invention having the above-described configuration, a loss of pressure that is generated in a confluence spool can be minimized through expansion of an open area of the confluence spool in the case of singly driving a working device such as a boom rather than in the case of a combined operation of working devices.

Claims (2)

1. A method for controlling a hydraulic system for a construction machine including first and second hydraulic pumps connected to an engine, a pilot pump, first and second working devices connected to the first and second hydraulic pumps to be driven, operation levers for the first and second working devices outputting operation signals that correspond to the operation amounts, spools for the first and second work devices shifted by operations of the operation levers for the first and second working devices to control hydraulic fluid supplied to the first and second working devices, a main control valve having a confluence spool that makes hydraulic fluid of the second hydraulic pump and hydraulic fluid of the first hydraulic pump join together, a controller, first and second pressure sensing devices detecting operation signals of the operation levers for the first and second working devices, and an electro-proportional valve converting pilot signal pressure that is supplied to the confluence spool into secondary signal pressure corresponding to a control signal from the controller, the method comprising:
a first step of detecting pilot signals according to the operations of the operation levers for the first and second working devices through the first and second pressure sensing devices and transmitting the detected pilot signals to the controller;
a second step of determining whether the operation is a single operation of the operation lever for the first working device;
a third step of supplying secondary signal pressure by the electro-proportional value to the confluence spool to expand an open area of the confluence spool with respect to the same operation pressure of the operation lever for the first working device and discharging hydraulic fluid discharged from the second hydraulic pump in proportion to the operation amount of the operation lever for the first working device if the operation lever for the first working device is operated to exceed a determined section in the case of singly driving the first working device due to the single operation of the operation lever for the first working device; and
a fourth step of supplying the secondary signal pressure by the electro-proportional value to the confluence spool in proportion to the operation amount of the operation lever for the first working device and dividedly supplying the hydraulic fluid discharged from the second hydraulic pump to the first and second working devices in the case of performing a combined driving of the first and second working devices due to simultaneous operations of the operation levers for the first and second working devices.
2. The method for controlling a hydraulic system according to claim 1, wherein electronic operation levers are used as the operation levers for the first and second working devices.
US14/410,987 2012-07-16 2012-07-16 Method for controlling hydraulic system for construction machine Abandoned US20150330058A1 (en)

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GB2516804A (en) 2015-02-04
DE112012006705T5 (en) 2015-05-28

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